1,3-Propanediol (also hereinafter termed “PDO”) is a monomer useful in the production of a variety of polymers including polyesters, polyurethanes, polyethers, and cyclic compounds. Homo and copolyethers of polytrimethylene ether glycol (hereinafter termed “3OPG”) are examples of such polymers. The polymers are ultimately used in various applications including fibers, films, molded products, etc.
U.S. Pat. No. 6,720,459 describes a continuous process for the production of polytrimethylene ether glycol from 1,3-propanediol. U.S. patent application Ser. No. 2002/0007043 describes the production of polytrimethylene ether glycol and copolymers thereof. U.S. Pat. No. 3,326,985 describes a method for producing polytrimethylene glycol from trimethylene glycol having an average molecular weight of 1200 to 1400. U.S. Pat. No. 2,520,733 discloses a process for the production of polymers of trimethylene glycol in the presence of a dehydration catalyst. Homogeneous catalysts, such as sulfuric acid, have historically been used in the preparation of polytrimethylene ether glycol, requiring purification of the product glycol from the catalyst.
The present invention provides an improved process for the production of polytrimethylene ether glycol and copolymers thereof in the presence of at least one ionic liquid.